1. Field of the Invention
The present invention relates to a hardening tool that utilizes semiconductor laser.
2. Description of the Related Art
For example, Japanese Patent Application Laid-Open Publication No. 2003-138314 (patent document 1) discloses a laser hardening device proposed by the present applicant. Further, Japanese Patent Application Laid-Open Publication No. 2005-238253 (patent document 2) discloses a laser hardening tool capable of being attached in removable manner to a tool post of a machine tool.
According to these laser hardening tools, the laser beams output from a laser emission source such as a semiconductor laser bar or a semiconductor laser stack are transmitted via an optical fiber or a waveguide to a torch disposed at the end of the tool.
As shown in FIG. 10, the prior art laser beam waveguide 10 has an inner surface 12 formed of a cylindrical surface. Since the laser beams LB traveling through the waveguide having the cylindrical surface 12 rotate along the cylindrical surface, the number of reflections is increased. Since the reflectivity of the inner surface of the waveguide is 1.0 or smaller, the efficiency is deteriorated each time the beams are reflected, which causes the laser output to be reduced.
The present inventors have conducted various experiments on the effect that the cross-sectional shape of the optical waveguide has on the laser output efficiency, and confirmed that an optical waveguide 20 with a rectangular cross-section having its inner surfaces formed of planar surfaces 22 has reduced number of reflections, and thus realizes an optical waveguide having high output efficiency.